Generating harmonic currents



March 4 1924. 1,485,650

H. J. vENNEs GENERAT ING HARMONI C CURRENTS /M vena/c' #wref/a JTVen/ves y is of general application in the electrical.

- vshowing operating characteristics of a thermionic device accord' `ofthis invention, the impressed wave is 'which may be resolved into afundamental ma be amplified.

4circuit arrangement for the production of tron source,

Patented Mar. 4, 1924. l UNITED STATES PATENT OFFICE.

HARALD J. vENNEs, or NEw YORK, N. Y., ASSIGNon 'ro WESTERN ELECTRICcourANY,'1NcoRroR.a'rEn, or NEW voRx, N. Y., A CORPORATION or NEW YoRx.

GENERATING HARMONIC CURBENTS.

V.Application lcd April 28, 1919. Serial No. 293,055.

To all whom t may conce/rn.' normal characteristic curve of a thermionicBe it known that I, HARALD J. VENNES, relay, it is seen that along onlya relatively a citizen of the United States, residing at short portionof the curve in the region New York, in the county of New York Landrepresenting zero potential on the grid will State of New York, haveinvented certain a given change of grid potential in the nega.- new anduseful Improvements in Generatl tive .and in the positive directionproduce ing Harmonic Currents, of which the fol- Substantially equalvariations in plate curlowing is a full, clear, concise, and exact rentabove and below a mean value. When description. the grid potential isvaried over a com- This invention relates to the generation parativelyWide range, the plate current of electric currents and has for an objectVariations d0 IlOt COIieSpOnd precisely, and the production of harmoniccurrents from a advantage-'may taken of this fact to sesource ofalternating voltage, cure a non-sinusoidal plate current by im- Afeature of the invention relatos to a pressing a sinusoidalelectromotive force of circuit arrangement whereby harmonics areSllloieilt magllltude- This action has been generated effectively by theuse-of an elcc- Called overloading the tube, and the distron dischargerela torting effect depends upon the limited sup- This invention relares to a means of andv ply'iof electrons present in the electron tube,method for producing harmonics from an available for conveying currentacross the impressed electromotive force of preferablysubstantiallysinusoidal wave form. The ap- According to the presentinvention a Chaiaratus is termed a harmonic producer and actllstlc ShQWna? Curve 2 1S Secured: m which the distortion is very pronounced, arts.o, It is herein considered in connection and which is Particularlyadapted t0 the with a transmission system as a generator orP1`0d110t1011 0f h91`m01110 0n 210001111@ 0f ,h regenerator, accordingas it is adapted to abrupt break 111 the P01431@n 0f the Cllrveln'produce harmonic currents for transmisfllcated by Tb@ l'aSO'll for*311,13 bend Sion Purposes, .or to Supply corresponding in the curve isprimarily,I that the internal harmonics for reception or retransmissionresistance is of such a small value relative purposes. According to thevpreferred forni Y later pre ominates in controlling the ampligiven amarked distortion in one half-cycle, tude 0f the .Plate Qmzrent- In .Fi,2 are hown the characteristic curve 3 an a curve while it is repeatedlmore nearl true to S form in the op osite half-cycle y taking 5 glvmgthe form 0f Wave Produced m the advant e of tlie irregularcharacteristic of an e ectron discharge de vice when provided with asuitable high v'resistance in its output circuit. The output current ofthe electron discharge device willtherefore have a distorted ornon-sinusoidal wave form,

sine wave form indica by the dotted curve tially sinusoidal, while theupper portion is much distorted. By analysis, it is found both even andodd harmonics, in about. the same proportion.-

. Referring to Fig. 3, current from a sine wave generator 6 of basefrequency is supplied through line 7 to the primary 8 of a ference. ismade to the drawings, in step-upY transformer, 'the secondary 9 of 1 and2 of which are 'ven curves whichfis connected to the input terminals off uency component and a series of sinusoi al harmomcs. By suitablecircuit arran ments, these harmonic currents may be amp ied to a workcircuit, and, if desired,

Figs

10 comprises an evacuated container orl tube hot', filament 11, or'other elecl a plate orv anode 12 and a 'd the present. -in-4 lorimpedance controllingx lement 13. A atter 14 maybe used to thenorfmalpotenf to the invention, and Fig. 3 illustrates iagrammaticallya' containing a harmonics according to veiition. f

From the curve 1 which represents the discharge space.

tothe lar e external fixedresistance that thel output circuit by an imressed potential of...

a 'therinonic' amplifier 10. The vamplifier 4. It is seen that theportion of curve be low the normal amplltude line 1s substanthat theoutput wave thus obtained contains ti of the 13. vThe lament 11 may be11 heated by current from a battery 15 regulated by the variableresistance 16. AThe amplifier' is provided with plate current from abattery 17, connected to the filament 11, and to the plate 12 through animpedance 18, which acts to exclude the variation current component fromthis path. The output circuit .of amplifier 10 is traced through acondenser 19 of large capacity to the grid 21 of the harmonic generatoror regenerator 20, which has a hot cathode or filament 22 connected tothe filament 11 and supplied with heating current from the battery 15. Aswitch 20 is shown whereby the normal potential of the grid relative tothe filament may be made zero as in the position shown, or may be 4madepositive or negative by throwing the switch to one or the other of theother positions indicated. Connected across the filament 22 and grid 21is a parallel resonant circuit 26 consisting of an inductance and acapacity tuned to the base frequency, so that this path offerspractically infinite impedance to the base frequency current, but lowimpedance to any harmonics which may have passed the amplier 10. Theresult is that a substantially pure sinusoidal wave is impressed uponthe harmonic gene ator or regenerator 20. Condenser 19 acts as ablocking condenser to prevent fiow of current from battery 17 throughpath 26 and back through the impedance coil 1S.

The harmonic producer 20 comprises an evacuated tube containing, inaddition to the grid 21 and filament 22 already mentioned, an anode orplate 23. Plate current is supplied from battery 17, connected to thefilament 22, and to plate 28 through an impedance coil 24, similar toimpedance coil 18, anda large ohmic resistance 25, which may beinductive or non-inductive. Coil 24 may be omitted, especially if theresistance 25 is inductive. This resistance 25 is large compared withthe normal output impedance of the tube, values of the order of from6000 ohms to 48000 ohms having been used, depending upon operatin 5conditions, where the normal internal output impedance of the tube wasof the order of 4000 or 5000 ohms. The smaller value of resistancementioned was used in a particular case in which the base frequencycurrent supplied to the harmonic generator was relatively strong, andthe large value Was used when the incoming base frequency current wasweak and it was found advantageous to bring the break in thecharacteristic of the generator well within the range of the smallimpressed potential. These values are given by Way of illustration onlyand are not to be construed as in any sense limiting the invention.Resistance 25, in addition to giving the highly advantageouscharacteristic for the production of harmonics, performs the additionalfunction of greatly stabilizing the output circuit, since when the tubeis highly conducting, i. e., when the distortion occurs and thereforewhen the harmonics are being produced, the impedance of tli'e circuit ispractically the impedance of the exterior portion of the circuit, andsmall fluctuations in the tube impedance, such as are often occasionedby an exchange of tubes, have negligible effect upon the production ofharmonics.

Y The output circuit of the harmonic generator 20 leads through thecondenser 27 of large capacity to the grid 28 of a thermionic amplifier80. which has a hot cathode or filament 20 connected to filament. 22 andsupplied with heating current from the battery 15. A battery 31 is usedto fix the normal potential of the grid 28. Condenser 2T acts as ablocking condenser to prevent fiow of current from battery 17 throughthe path 24, 25, and back through the inductance 34, mentionedhereinafter. In the evacuated enclosure of amplifier 30, besides thegrid 28 and filament 29 already mentioned, is a plate 32 connected tothe plate battery 17, through in'ipedance coil 33, which acts similarlyto impedances 18 and 21, to prevent fiow of variation current componentsin the plate battery circuit. Across the input terminals of theamplifier 30, an inductance 34 is connected, which offers low impedanceto the base frequency current component, but high impedance to theharmonics which appear in the output circuit of the harmonic generator20. The harmonics are therefore impressed on the amplifier 30, and afterpassing through the amplifier, they are led through a condenser 235 oflarge capacity to the primary 530 of a suitable transformer,thesecondary 3T of which may be connected to the desired work circuit. J

Although an exact explanation of the action of the resistance 25 isnotessential to enable one to practice this invention, thel followingexplanation is believed to be correct andimay assist somewhat in anunderstanding of the invention. It is not intended as a limitation onthe invention, Which is independent. of the theory of operation.

The space current circuit comprises in series the space current source,the large fixed external resistance and the variable internal resistanceof the tube. This latter resistance approaches a zero value as the gridpotential increases. As the internal resistance approaches zero thespace current; approaches the limiting value determined by the fixedexternal resistance. Accordingly. the bend in the characteristic curvemust occur between this limit -when the effect of the externalresistance preponderates and the other limit When the internalresistance is large enough to cause its effect to preponderate. Thatthis bend due to the effect of the large external resistance becomescomparatively sharp as the horizontal portion of the curve is approachedfollows from the fact that with a uniform rate of decrease of theinternal resistance, the rate of change lof the ratio of external tointernal resistance progressively increases.

It should be noted also that the eiect produced by the externalresistance and the ordinary so-called saturation eiect are additive,which increases the sharpness `of the bend in the characteristic curve.

Although the invention has been illustrated and described in connectionwith a pecific circuit arrangement, it is to be unerstood that it isnot' to be limited either to the specilic arrangement as a whole or toits particular details, but only by the scope of the appended claims.

What is claimed is:

1. The method of generating harmonics in a system comprising incombination a source of alternating electromotive force, an

'electric discharge repeating device having a cathode, an anode and animpedance control element, and a high resistance in the output circuitof the repeatingdevice, which method consists in impressing on therepeating device from said source cyclically varying voltage whichalternates between limits chosen to include the knee of thecharacteristic curve of said repeating de-v.

chosen to include the knee of the charactery istic curve of saidrepeater.

3. A generator of harmonics comprising an electric discharge repeatingdevice having a cathode, an anode and an impedance control element, asource of substantially constant alternatin potential connected to saidcathode and said impedance control element, and a direct current sourceand a large impedance serially connected to said cathode and anode, theamplitude of said alternating potential being sufficient to cy- 5. Agenerator of harmonics comprising an electron discharge repeatercomprising an electron discharge device with an anode, a cathode and animpedance control element, an input and an output circuit for saidrepeater, a source of substantially constant alternating potential and apolarizing source connected to said input circuit, a

of element ar e compared to the minimum internal impeance of said deviceconnected serially in said output circuit whereby angular configurationis given to the characteristic curve representing the relation betweenthe potential of the impedance control element with respect to thecathode and the space current, the potentials impressed from saidalternating potential and polarizing sources being such that operationoccurs over that part of said characteristic curvel which includes theangular portion.

In witness whereof, I hereunto subscribe my name this 24th day of AprilA. D. 1919.

HARALD I. VENNES.

-source of s ace current and an impedance

